Is a Low Incidence Rate of Ventilation Associated Pneumonia Associated with Lower Mortality? a Descriptive Longitudinal Study in Iran

Background: Ventilator-Associated Pneumonia (VAP) is an important cause of morbidity and mortality in patients admitted to Intensive Care Unit (ICU). The current study conducted to estimate VAP incidence, attributable mortality and case fatality rate, cost, so related factors can affect the outcome in patients. Materials and Methods: In this descriptive longitudinal study, demographic, clinical and para-clinical data were collected and attributable mortality and case fatality rate was estimated. Multivariable analysis was done to predict the possible risk factors on the outcome of VAP patients. Also, patients’ survival curve was plotted based on their length of ICU stay. Finally, the additional cost due to VAP in ICU was estimated. Results: Totally, 8% ICU admissions were affected by VAP and 4% expired during the ICU stay. Further, the attributable mortality rate of VAP was high as compared with standard mortality rate. The most case fatality rate was for Acinetobacter sp. (n=17 60.7%). In multivariable logistic regression analysis, age greater than 40 years, more than 96 hours mechanical ventilation and uncontrolled diabetes mellitus were predictor factors of higher mortality. Inverse association between survival time and ICU length of stay was reported. Finally, the additional cost of VAP was estimated of about 700 US$ per patients. Conclusion: According to the results, strategies to prevent mortality by reducing the duration of ventilation and ICU length of stay should be performed. Also, mandatory fees for the family and the healthcare system should be planned.

Intensive Care Unit, duration of hospital stay, and prior antimicrobial therapy. VAP is a serious, common and costly complication ranking first among nosocomial infections in ICU. Prevalence of VAP is between 9-27% and this mortality rate has been reported 30-70%. In some studies, the mortality rate of VAP is 16 to 20% (3)(4)(5)(6)(7).The risk of VAP in patients who are receiving MV increase 1-3% for every day of hospitalization. Different studies estimated the prevalence of VAP, 10.2% to 32% in 1000 person (5). Intubation, alone as a risk factor for pneumonia in hospitalized patients, is considered (6). There are several factors that increase the frequency of VAP including length of hospital stay, underlying diseases such as central nervous system, gastrointestinal tract infections, and multiple trauma, chronic lung disease, the supine position of the patient, surgery, chronic renal failure and the use of steroids (8)(9)(10). Also, unconsciousness, tracheotomy, multiple intubations during hospitalization, emergency intubation and nasogastric tube also affect the incidence of VAP (10,11). Although many studies indicate the low incidence of VAP following proper hand washing and use of protective gloves, but study on risk factors for mortality is limited.
Therefore, the aim of this study was to determine the incidence and mortality rate of VAP and related factors in a tertiary hospital in Iran.  To measure and predict prognosis of patients admitted to multicenter ICU the APACHE II score at first day of admission was used. According to standard table, mortality rate in score 0-15, 16-19, 20-30, and over 30 was 10, 15, 35 and 75%, respectively (15). According to this explanation, attributable mortality rate was estimated.       (18,19).

MATERIALS AND METHODS
Despite the low incidence, the death rate was almost high (41%). Some study estimated the frequency of VAP in care units specifically, 10 to 65% and the rate of mortality from 20 to 70% (7)(8)(9)20). Overall, rates of pneumonia are considerably higher among patients in ICUs compared with those in hospital wards, and the risk of pneumonia is increased 3 to 10 fold for the intubated patient receiving MV. Nevertheless, VAP is not always 'associated' with the ventilators but with the artificial airways (endotracheal tubes and tracheostomies cannulae) as well (21)(22)(23).
In this study according to APACHE II score, the VAP attributable mortality rate in ICU cases was about 34.7-37%, but this rate is variable and relies heavily on the underlying medical illness (20). Reports indicated mortality rate changes from 24 to 50%.
This survey, like most studies, has limitations such as the unavailability or incompleteness of certain data, recording of patient's vital signs by unskilled nurses with different precisions and some other restrictions. Although incidence rate and cost of length of ICU stay due to VAP is lower than many studies (24,30,33,34); however, due to high mortality and financial burden on the family and the healthcare system, practical steps should take for the prevention this disease.